Japanese Patent Publication No. 03792092 (PTL 1) is cited as background art. This patent describes “a method of evaluating a cosmic ray soft error tolerance of a semiconductor device comprising the steps of: dividing spectral distribution of cosmic ray neutrons into a plurality of energy bands respectively having a plurality of predetermined energy values as representative values; obtaining soft error partial cross-sectional areas of the semiconductor device corresponding to the plurality of energy values; and obtaining a sum of the soft error partial cross-sectional areas weighted with total fluxes of the respective energy bands, wherein a soft error rate of the semiconductor device in a prescribed actual use environment is estimated by using the sum of the soft error partial cross-sectional areas.”